The invention relates to systems and methods of thermally processing a substrate.
Substrate processing systems are used to fabricate semiconductor logic and memory devices, flat panel displays, CD ROMs, and other devices. During processing, such substrates may be subjected to chemical vapor deposition (CVD) and rapid thermal processes (RTP). RTP processes include, for example, rapid thermal annealing (RTA), rapid thermal cleaning (RTC), rapid thermal CVD (RTCVD), rapid thermal oxidation (RTO), and rapid thermal nitridation (RTN). RTP systems usually include a heating element formed from one or more lamps which radiatively heat the substrate through a light-transmissive window. RTP systems may also include one or more other optical elements, such as an optically reflective surface facing the backside of the substrate and one or more optical detectors for measuring the temperature of the substrate during processing. Many rapid thermal processes require precise control of substrate temperature over time.
The invention features a thermal processing method in which a temperature response of a substrate may be controlled during a heat-up phase or a cool-down phase, or both. This reduces the thermal budget of the substrate and improves the quality and performance of devices formed on the substrate. In particular, the inventors have realized that by controlling the rate of heat transfer between the substrate and a thermal reservoir (e.g., a water-cooled reflector plate assembly) during the thermal process, the temperature response of the substrate may be controlled.
In one aspect, the substrate is heated in accordance with a heating schedule and, during the heating schedule, the rate of heat transfer between the substrate and a thermal reservoir inside the thermal processing system is changed.
Among the advantages of the invention are the following. The results of certain thermal processing methods (e.g., methods of forming ultra-shallow junctions) are improved if the rates at which substrates are heated or cooled inside the thermal processing system are high. By changing the rate at which heat is transferred between a substrate and a thermal reservoir inside the processing chamber during the thermal process, the heat-up phase or the cool-down phase, or both phases, may be optimized to improve the quality of the devices produced. Temperature uniformity across the substrate is also improved.